And all across this country, in other states and other communities, as we said, it was an anxious monday, about something everyone has taken for granted. Millions of children returning to classrooms and some schools called in more security. There were even false alarms around the country, and here's abc's amy robach with that. Amy? Reporter: Diane, good morning and that's right -- good evening, excuse me. What happened here in newtown has brought sweeping changes to schools across this country on this first day back to class after the tragedy. Parents around the nation dropped their children off at school this morning. Many holding on a little more tightly. Have a good day. Reporter: A day of jitters. Schools from new york to tennessee to texas all went on alert after fear ignited several false alarms. Some bomb threats, others as minor as an umbrella mistaken for a gun. Turn around. It's closed. Reporter: An elementary school in richfield, connecticut, went into lockdown today after someone reported a suspicious person. Security on the minds of prince pams throughout the country today. It was a priority of sandy hook's own principal, dawn hochsprung, killed in the mass shooting. We spoke with her best friend and cousin. Safety was important to her. She was holding exercises and making sure people knew how to get out and to get out safely. Safety was her number one priority. She wanted school to be a safe haven, a place where students could come and just feel comfortable, like it was their second home. Reporter: Today, from coast to coast, principals were re-evaluating security and taking extra measures to protect their students, in pittsburgh, security guards now have guns. In this california school, the day started with a mock lockdown drill. Stay in lockdown mold until you hear an all clear announcement. Reporter: The other challenge for teachers and principals today, what to say to their students. We tell them that somebody was a very sick person, made some very poor choices and that is rare. That normally, usually, schools are safe places. Reporter: And in georgia, parents left nothing to chance, walking their kids all the way into school, hand in hand. And while some parents did keep their children out of school today, experts recommend getting your children back to a normal ree tune, as soon as possible. That is made, though, particularly difficult here in connecticut, where the governor has ordered a moment of silence on friday.

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